Air ventilation inlets, exposed to continuous air flow, may tend to become a collection point for dust and debris. Particles of foreign material collecting at the inlet area may lead to decreased airflow through the inlet and a reduction in total cooling efficiency. Less than desired cooling of an operating unit (e.g., a computer processor) may lead to decreased overall performance and less than desired results. Cleaning soiled inlet areas requires time and a possible shut down of a system for completion. Prior art filtration devices placed upstream of an air inlet achieve the desired result of keeping the air inlet clean but lack both the convenient layered aspect and the ability to be easily maintained or replaced.